I see them as mostly positive as long as you dont overly fixate on them. They provide a bit of replay value for me on some titles that I would not normally get out of them. The key to it is to only spend time on achevements that are fun and ignore the ones that are irritating. I personally hate collecting achevements.
Easy Points:
Bioshock
Mass Effect (time consuming)
Assassins Creed(repeditive)








